Drive for rotatable parts

ABSTRACT

A mechanical, play free drive for rotatable parts in particular in precision devices, which comprises a driven gear provided on the rotatable parts. A drive means drives the driven gear. A support element is in radial direction opposite to the driving means, and the driven gear is tong-like embraced by the drive means and the support element, for the most possible movement transmission free from forces.

United States Patent Ernst et al. [4 1 Dec. 12, 1972 [54] DRIVE FOR ROTATABLE PARTS 6] References Cited [72] Inventors: lgilnrsrgrtnsgez'il'ggjlr Jung, both of *U'mF TATEsjflTE 3,449,977 6/1969 Wilbur ..74/409 I 3,237,474 3/1966 Hawley et al ..74/410 [73] Ass'gnee' gg'sz g 'h gfggz'r ne'denhain 3,599,533 8/1971 Anthony ..74/410 x I 2] Filed: Nov. 16, 1970 Primary Examiner-Leonard H. Gerin 2| I AWL NW 89,926 Attorney-Ernest G. Montague [30] Foreign Application Priority Data [57] ABSTRACT A mechanical, play free drive for rotatable parts in :33 $3222 particular in precision devices, which comprises a y driven gear provided on the rotatable parts. A drive 52] us. c|....'..'. ..74/410 means hives the driven gear- A Support element is in [51] Int. Cl ..Fl6h 5.7/00 redial dheetieh PP he the driving means and the [58] Field of Search ..74/409, 410, 424.6 driven gear is tong-like embraced y the drive means and the support element, for the most possible movement transmission free from forces.

19 Claims, 12 Drawing Figures PATENTED HEB 2 I972 3. 705 51 8 sum 1 BF 7 Fig.2

IN VEN RS ALF ONS E T WERNER JUNG A TTE RNEY PATENTED DEC 12 I972 SHEET 2 BF 7 awn INVENTORS ALFONS ERNST W RNER JUNG ATTO NE'Y PATENTEDutc 12 I972 4 SHEET 3 OF 7 IN VFN TORS ALF S ERNST WER R JUNG A TTORNEY PATENTED DEC 12 I972 SHEET 6 UF 7 INVENTOIZS L ONS ERNST WRNR N BY E EJUG ATTORNEY 1 DRIVE FO RROTATABLE PARTS The present invention relates to a mechanical play free drive for rotatable parts, in particular at precision devices, by example, rotarytables,divisionhcads, etc.

drives, worm drives, friction drives or the like of known structure can be used at which two wheels engage each other. t

In known drives the drivinggear resiliently engages the drivengear provided at the part to beadjusted such, that a play free engagement is assured. Thereby, however, radial forces areexerted upon the part to be adjusted, which forces cause deformations onthe axle bearingand thus cause an impaired accuracy.

ltis, therefore, one object of the present inventionto provide a drive for rotatable parts of the type men- -tioned above, which create a multiple applicable drive and in which practically no radial forces are effective anymore onthe part to be adjusted and which enables nevertheless a play free and high precision transmission of motion without being expensive, disadvantageous as to the structure or even subject to disturbances.

It is another object of the present invention, to provide a drive for rotatable parts, wherein, for a transmission of motion which is free of forces as much as possible, a driven wheel, provided at the rotatable part,is tong-like embraced by a driving wheel and a support element, which latter is radially opposite the driving wheel. The driving wheel and the support element thereby equal but oppositely directed forces onto the driven wheel of the part to be adjusted.

Ina preferred embodiment of the present invention, a cranked driven wheel is provided on the rotatable part, the outside and the inner side of which cranked wheel tong-like, resiliently embraces the driving wheel and the support element. This arrangement results a mechanically and structurally advantageous design.

In known arrangements, to which the mechanical drive according to the present invention is to be applied (for example on precision rotary tables), in particular asymmetrically disposed weights on the rotatable part can cause distortions of the axle bearing which distortions impair the accuracy of true running.

It is therefore, still another object of the present inventionyto provide an arrangement with a rotatable part which avoids the drawbacks mentioned above, which shall assure at a high bearing capacity also a high accuracy, and which is to provide a particularly simple as 'well as rigid design. I

It is another object of the present invention to provide an arrangement of the type mentioned above, wherein between the precision axle bearing and a part rotatable by means of a particular support bearing, an axially resilient coupling is provided which is rigid radially and stiff against torsion. By insertion of a membrane between the precision axle bearing and the rotatable part it is avoided that forces effecting the rotatable part are also transmitted to the precision bearing adapted for the purpose of radially guiding the rotatable part. i

In the most simple case, the coupling between the precision axle bearing and the rotatable part can be a resilient metallic ring. 1

In a possible embodiment, according to the present invention, a flange is secured to the axle hearing or on ble part only by means of the membrane. The precision In order to drive the rotatable parts selectively gear axle bearing and the'support bearing for the rotatable the present invention.

With these and other objects in view, which will become apparent in the following detailed description, the present invention will be clearly understood in connection with the accompanying drawings in which the present'invention is disclosed by way of example only,

and in which:

FIG. 1 is a fragmentary axial section of a drive for rotatable parts, inv accordance with the present invention, disclosing a first embodiment thereof, wherein a driving wheel and a support element are provided which are disengagable by meansof a mechanical cam;

FIG. 2 is a section taken along the lines 1-1 of FIG. 1;

FIG. 3 is a fragmentary axial section of a drive for rotatable parts, in accordance with the present invention, disclosing a second embodiment thereof, wherein a swingably mounted driving wheel and support element are disengageable by electromagnetic means;

FIG. 4 is a section taken along lines 4-4 of FIG. 3; FIG. 5 is a fragmentary axial section of a drive for rotatable parts, in accordance with the present invention, disclosing a third embodiment thereof for a transmission of motion, which is free of forces and of high accuracy; 1

FIG. 6 is a fragmentary axial section of a drive for I rotatable parts in accordance with the present invention, disclosing a fourth embodiment thereof, for a transmission of motion which is free of forces and of high accuracy, whereby, however, the driving wheel and the support element are not disengagable;

FIG. 7 is a fragmentary axial section of a drive for rotatable parts, in accordance with the present invention, disclosing a fifth embodiment thereof wherein, a swingably mounted driving wheel and support element are disengagable by pneumatic means;

FIG. 8 is a section taken along the lines 8-8 of FIG.

FIG. 9 is a section taken along the lines 9-9 of FIG.

FIG. 10 is an axial section of a precision rotary attachment, whereby, for a transmission of motion, which is free of forces, to the rotatable part, the device of FIG. 7 can be used, and whereby in accordance with the present invention a resilient ring is disposed between an aerostatic axle bearing and the rotatable part which supports itself by means of a pivot bearing;

FIG. 11 is a schematical view of a safety circuit, which is designed of pneumatic elements, applicable to the device shown in FIG. 10, in connection with FIG. 7; and

FIG. 12 is an axial section of a rotary attachment with mechanical precision bearings for the rotatable part, disclosing a further embodiment, wherein, in accordance with the present invention the rotatable part is connected with the axle bearing by means of a resilient ring.

Referring now to the drawings and in particular to FIG. 1, the present invention is disclosed by example in connection with a precision rotary table to the rotatable table board 1 of which is secured a cranked gear 2, in which gear 2 engages a worm 3. The arrangement of a pair consisting of gear 2 and a worm 3 permits also a slight axial displacement of the part 1 to be adjusted. The worm 3 is rotatably mounted in a pillow block 4. The drive of the worm 3 takes place by means of an axle 5 (FIG. 2) by intermediate arrangement of nonrotating folded bellows.

At the side of the toothed wheel 2, which is opposite in radial direction of the worm 3, in accordance with the present invention, a support element 6 is provided, which in FIG. 1 is a pulley mounted with poor friction. The pillow block 4 for the worm 3 and the pillow block 7 for the support element 6 are play free and easily running displaceable on guides 8 and 9 by means of low friction bearings 10 and 11. Tension springs 12 disposed between the pillow blocks 4 and 7 bring about that the driving gear 3 and support element 6 are resiliently urged against the gear 2 such, that practically no radial forces can be effective on the part 1 to be adjusted.

For the purpose of disengaging the driving gear 3 and the support element 6, a cam 13 is provided in FIG. 1, which cam 13 is rotatable by means of an axle 14 and is capable of being locked by means of notches (not shown). The axle 14 of the cam 13 is immovably disposed in a part of the housing 15 of the round table, to which part of the housing 15 are also secured to the pillow blocks 16 and 17 of the guides 8 and 9.

In FIGS. 3 and 4, the supporting element 6 is provided on an angle-lever 16,, which is swingably mounted in the pillow block 4 of the driving gear 3 by means of an axle 17,. The pillow block 4 is swingably mounted in a fork 19 by means of axles 18. The fork 19 is screwed to the part of the housing 15. Tension spring 12 between the angle-lever 16 and the pillow block 4 cause that the driven wheel 2 is resiliently and tong-like embraced by the driving gear 3 and the support element 6.

For the purpose of disengaging the driving gear 3 and the support element 6, a lifting magnet 20 of a known type is provided, extendible pins 21 and 22 of which move in opposite directions the angle-lever 16 and the pillow block 4 until the driven wheel 2 can be rotated freely. The lifting magnet 20 is immovably secured to the part of the housing 15 by means of a holder 23.

FIG. 5 shows a play free drive of high accuracy for rotatable parts 1, in which also friction forces on the engaging gears exert no disturbing influence to the rotatable part 1, which can be moved slightly also in axial direction.

Deviating from FIG. 3, in FIG. 5 the support element 6 engages forcibly the inner side of the gear 2 Beyond that in FIG. 5 the fork 19 is movable in axial direction of the rotatable part 1 by means of a spring parallelogram 25, while the fork 19 is secured in axial direction of the driving gear 3 in predetermined manner.

The support element 6 is provided on an angular lever 16,, which latter is pivotally mounted in the pillow block 4, of the driving gear 3 by means of an axle 17,. The pillow block 4 is swingable in the fork 19 by means of axles 18 The spring parallelogram 25 which is immovably attached to the housing 15, of the device, consists in conventional manner of two leaf springs 26 and 27, which are secured to the lower side of the fork 19, by means of a distance member 28. The tension springs 12 between the angular lever 16, and the pillow block 4 resiliently press the driving gear 3 and the support element 16 against the driven gear 2 The lifting magnet 20 provided for the purpose of disengaging the driving gear 3 and the support element 6 is immovably secured to the housing 15 of the device by means of the holder 23.

Deviating from FIG. 5, in FIG. 6 a gear 2 is provided, instead of the toothed gear 2 in which gear 2 the worm 3 engages. The tension springs 12 press resiliently the driving gear 3 and the support element 6 against the cranked worm gear 2 The drive, disclosed in FIG. 6 and designed in accordance with the present invention, is then applied, when the driving gear 3 is to remain continuously in engagement.

In FIG. 7 the part 1 to be adjusted is rotatably mounted by means of aerostatic bearings. Further aerostatic support bearings are provided in an immovable part 30, on which aerostatic support bearings the part 1 to be adjusted supports itself, as is shown in FIG. 10, which will be described below.

A cranked gear 2 is secured to the part 1 to be adjusted in which gear 2 engages the driven worm 3. The support element 6 is disposed on an angle lever 16,, which is swingable in the pillow block 4,, for example, by means of point bearings 31 and 32 (FIG. 9). The pillow block 4 supports itself on leaf spring arms 33 and 34 (FIG. 8), which are secured to the housing 15 by means of a carrier body 35.

Folded bellows 40 are disposed on the angular lever 16 by means of a holder 36, which folded bellows project through a recess 37 in the pillow block 4 and is secured to a follower 38, which applies at the pillow block 4 of the worm 3.

In case compressed air is fed by means of the conduit 39 then the bellows 40 expand and the support element 6 is swung out until it engages to the inner side of the driven gear 2. By a further expansion of the bellows 40, the pillow block 4 is swung out by means of the follower 38 and the driving gear 3 is pressed against the driven gear 2, until the support element 6 and the driving gear 3 exert equal but oppositely directed forces onto the driven gear 2. Tension springs 41 and 42 between the follower 38 and the angular lever 16, cause, that the driving wheel 3 and the support wheel 6 are disengaged when the compressed air is switched off. Abutments 43 and 44 disposed on the angular lever 16,, limit the disengagement path. The tension springs 41 and 42 grip directly on the follower 38 and on the angular lever 16, by means of pins 45 and 46. The leaf springs 33 and 34 are jammed to the carrier body 35 and to the pillow block 4 by means of ledges 47 and 48.

FIG. 10 discloses as an example of an application a precision round table with aerostatic bearings, the rotatable part 1 of which engages the drive shown in FIG. 7.

The aerostatic bearing causing the radial guiding of the part 1 to be adjusted, comprises two spherical bearing parts 50 and 51, which are secured to a distancing disc 52. In the housing 53 of the bearing are provided air supply nozzles 54, which open into an annular channel 55 which channel 55 is bordered by a ring 56. The

l060l0 0l07 compressed air reaches the channel 55 by means of a conduit 57. The housing 53 of the aerostatic bearing is secured to a flange 58, which is screwed with the immovable lower part 30 of an aerostatic pivot bearing for the part 1 to be adjusted.

In FIG. a flange 59 is secured to the spherical bearing part 50 by means of a centering ring 60. The flange 59 is coupled with the part 1 to be adjusted only by means of a membrane 61. The membrane 61, which in the simplest case can be designed as a resilient metallic ring, is jammed to the part 1 and to the flange 59 by means of securing rings 62 and 63. By the intermediate arrangement of a membrane 61 between the part 1 to be adjusted and the aerostatic precision axle-bearing 50 and 51, a distortion of the high precision low friction bearing 50/51 is excluded, even in case of an asymmetrically disposed load on part 1.

In the part 30 of the aerostatic support bearing are provided several air feeding nozzles 65, which are dis tributed at the periphery and to which nozzles 65 compressed air is supplied by means of conduits 64. The stationary lower part 30 of the bearing is screwed together with the part of housing 15.

A centering ring 66 is screwed onto the spherical bearing part 51 (FIG. 10) and on the'centering ring 66 a division 67 is disposed by means of a socket 68. The division 67 can be read by means of an optical angular reading device 69 which is designed in known manner. In round table or the like in which no division of an angular reading device is provided on the rotary axle and in which the reading of the angle is carried out by means of an indication device coupled with the drive, particularly the drive as shown in FIGS.5 or 6 is suitable, which also permits a transmission of movement with high accuracy.

By the intermediate arrangement of the membrane 61 in the precision round table, shown in FIG. 10 it is avoided that forces effecting the part 1 to be adjusted are also transmitted to the precision bearing 50 and 51. Besides the drive, designed in accordance with the present invention, prevents, that disturbing radial forces effect on the part 1 to be adjusted of the precision round table of high carrying capacity.

FIG. 11 shows a safety circuit for the aerostatic precision bearings 50 and 51 and 65 of FIG. 10, to which air of different pressure is applied. By the safety circuit the pneumatic adjusting member 40 (FIG. 7) is only then effective, when pressurized air is applied simultaneously at both conduits 57 and 64 of the aerostatic precision bearings 50, 51 and 65, Thereby, are excluded damages of the precision bearings 50, 51 and 65, which damages would result upon rotation of part 1, when compressed air is lacking in the conduits 57 or 64.

The safety circuit is designed in the following manner:

The pressurized air of the feeding conduit 57 controls a valve 70, the passage for the pressurized air of the second supply line 64 of which is freed only in case pressurized air applies on both conduits 57 and 64. The compressed air, which passes through the valve 70, is fed to a manually operable valve 72 by means of a conduit 71, and is fed to the pneumatic adjusting member 40 by means of the conduit 39. A source of pressurized air is shown in FIG. 11, which delivers prepared air to the above described pneumatic system.

above a bearing 400, which flange 500, according the to the present invention, is coupled with the part 700 to be adjusted by means of a membrane 600. In FIG. 12 the membrane is designed as a resilient metallic ring, which can be clamped to the part 700 to be adjusted by means of securing rings 250 and 350. The part 700 to be adjusted supports itself on a ring 900, secured to the frame 100, by means of low-friction bearings 800.

By means of a socket 130, a division is disposed on the rotary axle 300, in the show embodiment. The division can be read by means of an optical angular reading device of known type.

By the intermediate arrangement of the membrane 600 between the part 700 to be adjusted and the precision axle bearing 200 a distortion of the bearing 200 of high accuracy is excluded, even in case of an asymmetrically arranged load on the rotatable part 700. Any of the .play free drives shown in FIGS. 1 to 7, which enable a transmission of motion free from forces, can be applied at the rotatable part 700.

While we have disclosed several embodiments of the present invention, it is to be understood that these embodiments are given by example only and not in a limiting sense, I

We claim:

1. A mechanical, play free drive for rotatable parts in particular in precision devices, comprising a driven gear provided on said rotatable parts,

a drive means driving said driven gear,

a support element being in radial direction opposite to said driving means, and

said driven gear being tong-like embraced by said drive means and said support element.

2. The drive as set forth in claim 1, wherein said drive means and said support element exert equal, oppositely directed forces onto said driven wheel of said rotatable part to be adjusted.

3. A mechanical, play free drive for rotatable parts in particular in precision devices, comprising a driven gear provided on said rotatable parts,

a drive means driving said driven gear,

a support element being in radial direction opposite to said driving means,

said driven gear being tong-like embraced by said drive means and said support element,

said drive means and said support element exert equal oppositely directed forces onto said driven wheel of said rotatablepart to be adjusted, and

a device for angle adjustment, in particular a precision rotary attachment of high loading capacity, which includes a precision axle bearing for rotatably mounting said rotatable part to be adjusted in radial direction,

a separate support bearing for mounting said rotatable part in axial direction,

a coupling between said precision axle bearing and said part being rotatable by means of said separate support bearing, and

said coupling being axially resilient, and rigid radially and against torsion.

4. The drive, as set forth in claim 3, wherein said driven wheel provided on said rotatable part is designed as a cranked wheel.

5. The drive as set forth in claim 4, which includes a swingable pillow block carrying said drive means,

and

an angle lever swingably mounted in said pillow block, and carrying said support element.

6. The drive as set forth in claim 5, which includes a tong-like means comprising said pillow block and said angle lever,

pneumatic means for the purpose of engaging the tong-like means,

spring means applying to said pillow block and to said angle lever, and adapted for disengaging said drive means and said support element.

7. The drive for an angle adjusting device, as set forth in claim 6, which includes an aerostatic precision axle bearing for rotatably mounting said rotatable part to be adjusted in radial direction,

a separate aerostatic support bearing for mounting said rotatable part in axial direction,

said drive applying at said rotatable part,

a pneumatic adjusting member for engaging of said drive means and of said support element,

two feeding conduits capable of supplying compressed air to said aerostatic bearings, and

said pneumatic adjusting member being operable only in case said compressed air is applied to both of said feeding conduits.

8. The drive, as set forth in claim 7, which includes a valve means arranged in a first of said feeding conduits for said aerostatic axle bearing, and controlled by said compressed air in said first feeding conduit,

a passage of said valve means for said compressed air in the second of said feeding conduits for said aerostatic pivot bearing, only being opened upon applying said compressed air to both of said feeding conduits,

a third feeding conduit provided between an outlet of said valve means and said pneumatic member for said drive means and said support member, and

a manually operable valve means interconnected in said third feeding conduit.

9. The drive as set forth in claim 5, which includes a spring means applying to said pillow block and said angle lever, adapted for engaging said drive means and said support element, and the disengagement of said drive means and said support element being performed selectively by an immovable mechanical cam means, a lifting magnet and a pneumatic means, respectively, and applying to said pillow block and said angle lever.

10. The drive, as set forth in claim 5, which includes resilient joint means provided for a play-free swinging of said angle lever for said support element and of said pillow block for said drive means.

11. The drive as set forth in claim 5, wherein said support means comprises a low friction roller.

12. The drive as set forth in claim 5, which includes a spring-parallelogram means displaceable in axial direction of said rotatable part and carrying said pillow block of said drive means swingable in direction to said driven wheel, for transmitting motion as free from forces as possible and with high accuracy to said rotatable and axially displaceable part, and wherein at least said support element engages forcibly said driven wheel. 13. The drive, as set forth in claim 3, which includes pillow blocks respectively receiving said drive means and said support element, a guide means provided for a straight displacement of said pillow blocks, and spring means applying at said pillow blocks for the purpose of engaging said drive means and said support element. 14. The device for angle adjustment as set forth in claim 3, which includes a membrane coupling said precision axle bearing and said rotatable part. 15. The device for angle adjustment as set forth in claim 14, which includes a flange means secured to said precision axle bearing and a rotary axle respectively, and said flange means connected to said rotatable part by means of said membrane. 16. The device for angle adjustment as set forth in claim 3, which includes a resilient metallic ring disposed between said precision axle bearing and said rotatable part. 17. The device for angle adjustment as set forth in claim 3, wherein said precision axle bearing and said support bearing, which supports the rotatable part in axial direction, comprise aerostatic bearings. 18. The device for angle adjustment as set forth in claim 17, which includes a rotatable bearing part of said aerostatic precision axle bearing guided in radial as well as in axial direction, and a division for an angle measuring device disposed on said rotatable bearing part. 19. The device for angle adjustment as set forth in claim 17, wherein said aerostatic precision axle bearing comprises two rotary-symmetrical bearing parts, said bearing parts are interconnected by means of a distancing member, and are adapted to complement a housing, and, wherein one of said bearing parts is coupled with said rotatable part by means of said membrane, while the oppositely disposed bearing part is connected with said division of said angle measuring device. 

1. A mechanical, play free drive for rotatable parts in particular in precision devices, comprising a driven gear provided on said rotatable parts, a drive means driving said driven gear, a support element being in radial direction opposite to said driving means, and said driven gear being tong-like embraced by said drive means and said support element.
 2. The drive as set forth in claim 1, wherein said drive means and said support element exert equal, oppositely directed forces onto said driven wheel of said rotatable part to be adjusted.
 3. A mechanical, play free drive for rotatable parts in particular in precision devices, comprising a driven gear provided on said rotatable parts, a drive means drIving said driven gear, a support element being in radial direction opposite to said driving means, said driven gear being tong-like embraced by said drive means and said support element, said drive means and said support element exert equal oppositely directed forces onto said driven wheel of said rotatable part to be adjusted, and a device for angle adjustment, in particular a precision rotary attachment of high loading capacity, which includes a precision axle bearing for rotatably mounting said rotatable part to be adjusted in radial direction, a separate support bearing for mounting said rotatable part in axial direction, a coupling between said precision axle bearing and said part being rotatable by means of said separate support bearing, and said coupling being axially resilient, and rigid radially and against torsion.
 4. The drive, as set forth in claim 3, wherein said driven wheel provided on said rotatable part is designed as a cranked wheel.
 5. The drive as set forth in claim 4, which includes a swingable pillow block carrying said drive means, and an angle lever swingably mounted in said pillow block, and carrying said support element.
 6. The drive as set forth in claim 5, which includes a tong-like means comprising said pillow block and said angle lever, pneumatic means for the purpose of engaging the tong-like means, spring means applying to said pillow block and to said angle lever, and adapted for disengaging said drive means and said support element.
 7. The drive for an angle adjusting device, as set forth in claim 6, which includes an aerostatic precision axle bearing for rotatably mounting said rotatable part to be adjusted in radial direction, a separate aerostatic support bearing for mounting said rotatable part in axial direction, said drive applying at said rotatable part, a pneumatic adjusting member for engaging of said drive means and of said support element, two feeding conduits capable of supplying compressed air to said aerostatic bearings, and said pneumatic adjusting member being operable only in case said compressed air is applied to both of said feeding conduits.
 8. The drive, as set forth in claim 7, which includes a valve means arranged in a first of said feeding conduits for said aerostatic axle bearing, and controlled by said compressed air in said first feeding conduit, a passage of said valve means for said compressed air in the second of said feeding conduits for said aerostatic pivot bearing, only being opened upon applying said compressed air to both of said feeding conduits, a third feeding conduit provided between an outlet of said valve means and said pneumatic member for said drive means and said support member, and a manually operable valve means interconnected in said third feeding conduit.
 9. The drive as set forth in claim 5, which includes a spring means applying to said pillow block and said angle lever, adapted for engaging said drive means and said support element, and the disengagement of said drive means and said support element being performed selectively by an immovable mechanical cam means, a lifting magnet and a pneumatic means, respectively, and applying to said pillow block and said angle lever.
 10. The drive, as set forth in claim 5, which includes resilient joint means provided for a play-free swinging of said angle lever for said support element and of said pillow block for said drive means.
 11. The drive as set forth in claim 5, wherein said support means comprises a low friction roller.
 12. The drive as set forth in claim 5, which includes a spring-parallelogram means displaceable in axial direction of said rotatable part and carrying said pillow block of said drive means swingable in direction to said driven wheel, for transmitting motion as free from forces as possible and with high accuracy to said rotatable and axially displaceable part, and wherein at least said support element engages forcibly said driven wheel.
 13. The drive, as set forth in claim 3, which includes pillow blocks respectively receiving said drive means and said support element, a guide means provided for a straight displacement of said pillow blocks, and spring means applying at said pillow blocks for the purpose of engaging said drive means and said support element.
 14. The device for angle adjustment as set forth in claim 3, which includes a membrane coupling said precision axle bearing and said rotatable part.
 15. The device for angle adjustment as set forth in claim 14, which includes a flange means secured to said precision axle bearing and a rotary axle respectively, and said flange means connected to said rotatable part by means of said membrane.
 16. The device for angle adjustment as set forth in claim 3, which includes a resilient metallic ring disposed between said precision axle bearing and said rotatable part.
 17. The device for angle adjustment as set forth in claim 3, wherein said precision axle bearing and said support bearing, which supports the rotatable part in axial direction, comprise aerostatic bearings.
 18. The device for angle adjustment as set forth in claim 17, which includes a rotatable bearing part of said aerostatic precision axle bearing guided in radial as well as in axial direction, and a division for an angle measuring device disposed on said rotatable bearing part.
 19. The device for angle adjustment as set forth in claim 17, wherein said aerostatic precision axle bearing comprises two rotary-symmetrical bearing parts, said bearing parts are interconnected by means of a distancing member, and are adapted to complement a housing, and, wherein one of said bearing parts is coupled with said rotatable part by means of said membrane, while the oppositely disposed bearing part is connected with said division of said angle measuring device. 